Cylinder tuning of cavity



y 8, 1956 E. BARTON 2,745,070

CYLINDER TUNING or CAVITY Filed Jan. 8, 1945 ll WM J W F ATTORNEYCYLINDER TUNING F CAVITY Loy E. Barton, Collingswood, N. 1., assignor tothe United States of America as represented by the Secretary of the NavyApplication January 8, 1945, Serial No. 571,921

9 Claims.- (Cl. 333-82) The present invention relates to a tuningarrangement for an electrical resonant chamber adapted to be used atultra high radio frequencies.

An .object of the invention is to provide an electrical resonatoradapted to accommodate a lighthouse tube and equipped with a simple andefiicient tuning arrangement for the resonator. e

Another object is to provide a continuously variable tuning cylinder foruse in an electrical resonant chamber adapted for use in a highfrequency radio system.

As is known in the art, a lighthouse tube is a disc-seal electronicvacuumtube for use at ultra high frequencies above 500 .megacycles, inwhich the grid and anode connections protrude through the glass envelopein the form of parallel metallic rings spaced from one another along thelength of the tube. The cathode is coupled to an outer metallic shellfor the radio frequency current. One such lighthouse tube, mentionedbyway of example only, is the General Electric type 446 triode. andillustration of this type of tube is given in the Science News Letterfor August 19, ,1944, page 115, and in the copending application ofGoddard I et al., Serial No.

487,722, filed May 20, 1943, now Patent No. 2,515,213.-

A description of the invention follows in conjunction with adrawing,wherein:

Fig. 1 illustrates in cross-section the electrical resonant chamber andtuning arrangement of an embodiment of the invention;

Fig. 2.illustrates a side view of Fig. 1, partly broken away, takenalong the line 22 of Fig. 2; r

Fig.3 illustrates the details of the tuning cylinderof Fig. l; and. .3

Fig. 4 illustrates the springy metallic washer used between the endplates. of the cylinder of Fig., 3 and the walls of the resonantchamber. v

The resonant chamber of Fig. l-is especially designed to accommodate alighthouse? vacuum tube. The resonant chamber comprises ,a cylindricalmetallic wall 1 A description electrically closed by metallic end'plates 2 and 2. The

end plate 2 is provided with a circular opening or aperture 3. forenabling the grid and anode rings of the lighthouse tube (not shown) toenter its interior. Concentrically positioned around circular aperture 3and connected to end plate 2 is a metallic cylinder 4 which is providedat, its open end with annularly arranged metallic contact fingers 5 forengaging the metallic cathode shell of the lighthouse tube. Also mountedon end wall 2 inthe interior of the resonant chamber but insulatedtherefrom, froma direct current standpoint, by means of'a micainsulation ring 6, is an annularly arranged ring of-metallic contactfingers 7' for engaging the grid ring of the lighthouse tube. I

Contact fingers 7 and contact fingers, 5 are resilient in"character'toenable the lighthouse tube to be easily inserted into the resonator andto assure good electrical contact with the vacuum tube elements.

A cylindrical metallic tube 8 is fastened to the conshaft 14 as to causethe solid section B illustrated in Fig. 1 to be nearest to the tube 8,in which case the H resonant chamber. detail in Fig. 4. I

Polarizing potential for the anode of the lighthouse 2,745,070 PatentedMay 8, 1956 ICC tact fingers 7 by means of a metallic flange 9, in turnsoldered to the tube 8. It will thus be seen that metallic tube 8 formsan extension, so to state, of the grid contact arrangement -7. A blockof insulation 10 serves to clamp the assemblage of contact fingers 7 andmetallic tube 8 to the end plate 2 of the resonant chamber.

tube 11 and plate 12 to the end plate 2'.

For tuning the electrical resonant chamber there is provided in theinterior of the chamber a rotatable metallic cylinder 13 which is cut toleave approximately one-half ofthe wall area. This is shown in moredetail in Fig. 3. Tuning cylinder .13 is provided with metallic endwalls 13'. One end wall 13' is provided at its center with a round stubwhich passes through an aperture in the end plate 2 of the resonantchamber, while the other end wall 13' is provided at its center with around shaft 14 which passes through an aperture in end plate 2 of thechamber. The cylinder is rotated by means of shaft 14. Tuning cylinder13is provided with a wedge-shaped slot S in order to provide a linearrelation between the change in frequency and angular rotation of thecylinder.

Positioned between each end wall 13 of the tuning cylinder and theadjacent end plate 2 or 2' of the chamber is a metallic resilient ring15 having a multiplicity of springy segments in order to assure goodelectrical contact between the cylinder ends and the end plates of theResilient ring 15 is shown in more tube is supplied from a metallic stub16 (note Fig. 2) which is connected to the metallic tube 11 through achoke coil 17. Metallic, stub 16 is insulated from the resonant chamberby means of an insulation bushing, not shown. 1

A condenser is formed by the insulation ring 12 which insulates themetallic tube 11 from the endplate 2' of the resonator. condenser fordirect current, and serves to by-pass energy of the operating frequencyfrom the anode electrode of the lighthouse tube to the end plate 2 ofthe resonator.

A condenser isalso-formed by the insulation ring 6 and this condenser iseifectively coupled across the grid and cathode of the lighthouse tube.The value of this condenser determines the amount of radio frequencyvoltage supplied to the grid relative to that generated on the anode. g

The resonant chamber, together with its associated uary 8, 1945, forLighthouse Tube Oscillator, now Patent No. 2,627,577, in which case agrid return choke in the form of a wire about one inch long should be. I

connected between the metallic tube 8 and the cylinder wall 1 of theresonator. 1

In the operation of the tuning mechanism of the invention, thetuningcylinder 13 may be so rotated by approximate efiective length of theresonant chamber is given by dimension L1. In this position, the currentpath along the inside of the resonator is the shortest, the inductanceof the resonator is at its lowest value,

In effect, this condenser is an isolating L2,-'lin which positionthecurrent path along thosinsider 5 of th'e-resonatoris the longest,tl1e="inductance-= of the resonator will' be at-itsgreatest value;and"the =fr"equency= at '-'itslowest. At intermediate positions; the:current paths will be-differenbftomthe two above extremes, and

the frequency-of operation will be between: the highest and" lowestvalues:

The larger'the cylinder 13*is-with respect to the'cavity of th'echamber, the greater-will 'be 'thetuning'ran'ge':

One advantage of the presentinventiom is that the cylinder andshaftarrangement eliminates theneed for 15 complicated screw and slidingarrangements used in moreconven-tional tuning systems:

Other advantages lie in thefact that Y the system 1 is dustproof whenthe vacuum"tube is inserted; and there is -no b'ack lash presentWhen'the cavity is tuned.-

In one experimental embodiment of the-invention; the Y resonant chamberand tuning arrangement "of Fig. lwasa used in an oscillator circuitemploying a lighthouse tube to generate oscillations of a frequencyabove- 500 megacycles, and a wide tuning range of morethan 100megacycles wasobtained.

It should be noted that the resonant chamber; by virtue of 'the metallicextension tube 8} approximates a concentric line 'resonatorin form, andfor this reason it should be-understoodfthatthe' invention-is notlimited to the particular configuration of resonator illustrated.

What is claimed is:

l. A tuning element for an. electrical resonator comprisingarotatablemetallic cylinder having; half the cylindrical surface area cutaway and'having a wedge-- shaped cut in the non-cut away area thereof.

2. An electrical resonator for use at ultra high-fre quencies andadapted to'accommodate alighthouse *tube, comprising a cylindricalmetallic Wall' provided with' metallic end plates, one of said endplates having a circular aperture therein; a metallictube mountedbmtheoutsidewof said one end plate-in concentric'relation to said aperture,said metallic tube having-annularly'arrangedcontact fingers for"engaging the cathode shell of 1 the lighthouse tube, andanother-metallictubefastened to said one end plate in the interior ofsaid resonator" and also arranged in concentric relation tosaidapertnre', said lastmetallic'tube being providdwith annularcon tactfingers for engaging the grid ring of said lighthousetube; and "a thirdmetall'ic tube -mounted coaxiallyrela tiveto' said aperture but 'locatedin' the interior of said' chamber and secured to. the other end plate ofsaid' chambenfor engaging the anode electrode of saiddight. house tube;and a tuning element inside 'said chamber; said tuning elementcomprising a rotatable metallic cyl inder'h'avinganappreciable portionof its surface area cut away, the axis ofrotationof said cylinderbeingparallel to the axes of said metallic tubes, the ends of" said'rotatable cylinder beingselectricallyconnected to'the 6 prising a=rotatabletzmetallic cylinder having -half the cylindrical'snrfaceareathereof-cut away-"and a-wedgeshaped slot-cut in=the non-cut away surfacearea thereof symmetrically positioned about a plane=perpendicular to'the: :axis :of' rotation 1 thereof.

4'. An electrical resonator comprising a substantially 7o closed"cavitystructure having a dimension which deter-- mines the resonantfrequency-thereof; and means for-- varying said dimension comprising ahollow semi-cylindrical. member having alt-length dimensionsubstantiallyequal to the cavity dimension perpendicular'to said dimension rotatablymounted within the cavity about an axis perpendicular to said dimensionand asymmetrically positioned with respect to the cavity.

5. An electric resonatorrcornprising a substantially closed cavitystructure having a dimension which determines theresonantfrequencythereof, and -means for varyingwsaid dimensioncomprising awhollowt semi-.cylin; drical member having ;azlengthdimensiom-substantially equal to the cavity dimension perpendiculartoasaidtd'tmension .rotatably, mounted within the cavity about an axisperpendicular-to said' dimension" and "asynnnetrically positioned withrespectrtortheacavity and said member having a wedge-shaped slot cut inthe surface thereof symmetrically positioned with respect to a planeperpendicular to said axis.

6; Anelectrical resonator-comprisinga substantially closed" cavitystructure having "-a" dimension-which deter mines the resonantfrequencydh'ereof," and -means for varying" said dimension "comprising'a -hollow cylindrical member having a length dimension substantiallyequal to" i the" cavitydimension perpendicular to" said dimension"rotatably mounted within the cavity about an axis 'per-' pen'd'icular tosaiddimension' and asymrrtetricall'y' positioned *With respect to thecavity; said cylindrical member" having anappreciable' portion ofthe-surfaicearea' thereof cut'awayi" I 71Anelectrical resonatorcomprising a substantially" closed cavity structure 'having'a' dimensionwhich" deter= mines the resonanrfr'equency thereof; and 'meansfor"varying said" dimension" to tune the cavity comprising a hollowcylindrical member having'a'length' dimension substantially equal to'the cavity dimensionperpendicular to said dimension rotatablygmountedwithin thecavit'yaboutan'axis perpendicular to'said dir'nension'andasymmetrically pOS ffiOn'cdWiflT respect to the cavity,saidcylindrical member having an appreciable" portion of the surface*area K thereof" cut away and a wedge shaped'isl'ot cut in daemon-cutaway surface-area thereof symmetn'c'ah lyposifioned with" respectto' aplane perpendicular to. said axis.

8. In" anelectrical resonator; a substantially closed. cavitystructure;a'-hollow"conductor position'edfin' said cavity perpendicular to onedimension thereof, andrneans'" for tuning the cavity; the last-namedmeans comprising a hollow semi-cylindrical'-'memberhaving' a lengthdimension=substantiallyequal to said'one dimension rotatably mountedwithin the cavity in spaced' relation from the' con'ductor' about anaxisparallel thereto:

9'. Iii-' an electrical resonator; asubstantially closed" cavitystructure, a hollow conductor positioneddmsaid cavity perpendicular toone dimension thereof; andmeans fortuning'the -cavity comprising ahollow "semi-cylindricalmember having a length dimensionsubstantially'equal 1 to said one dimension rota-tablymountedwithinsth'e" cavity in spaced relationfr'om' the conductor about an'axis' parallel thereto; and saidmember having -a wedgoshaped slot cutin the='surface thereofsymmetrically,positioned" with respect to aplaneperpendicular tosaid 'axis:

References =-(Iitedain the file *of th'is patent UNITED STATES" PATENTS1,632,709 Miller. mumm -192;? 1 2,153,205 Bark.-. Apr. 4,--,19.39.-*2,355,088. Lavoie ...A -ugg 8;,1944 442,671 Tompkins -n.June:-'1,,19.48i

FOREIGN PATENTS 4585710 Great Britain Dec. 24,,1936

